CELL MOTILITY IN TUMOR INVASION Our overall objective is to understand how dysregulation of cell migration contributes to tumor cell invasiveness in prostate cancer. Cell motility signaled by integrins and growth factor receptors promotes invasion, making this an attractive target for intervention. However, the roles of underlying biophysical processes of motility have not been dissected. Recent advances in our understanding of the biochemical and biophysical controls of motility now enable us to ask whether these cell processes are critical for tumor invasiveness. Our central hypothesis is that prostate tumor cell invasiveness can be inhibited by interfering with specific motility-associated signaling pathways that govern critical biophysical processes. At least two major biophysical processes are primary governors of cell locomotion: (1) cell/substratum adhesiveness, and (2) cell contractile force. We will employ a set of model cell types to test key hypotheses. These include androgen-independent prostate tumor cells of differing invasive potential as well as a fibroblast system to parse signaling pathways. Our quantitative, integrated-systems engineering approach to cell migration will determine whether targeted disruption of specific motility-associated signaling pathways and cellular processes can block tumor invasiveness. Aim I will test the hypothesis that de-adhesion of the cells' trailing edge is required for prostate tumor cell invasiveness, and that calpain is an operative molecular target for inhibitory intervention. We found that calpain-mediated de-adhesion is required for fibroblast locomotion in both integrin-induced and EGF-stimulated motility, making this intracellular protease an attractive target. However, it remains to be determined both whether tumor cell motility is governed by calpain-mediated de-adhesion and whether blocking this step, and preventing decreased adhesion, will prevent tumor invasiveness. Aim II will test the hypothesis that cell contractility is necessary for prostate tumor cell invasiveness, and that myosin light-chain kinase is an operative target for inhibitory intervention. Cell locomotion requires internal contractile forces to translocate the cell body and trailing edge. MLCK is a regulator of contraction and is thought be important for integrin-induced motility at the least. It needs to be determined, therefore, whether this is also an important regulator for the EGFR-mediated response. The successful completion of these Aims will provide new targets for rationale therapeutic interventions aimed at the critical stage of tumor progression to invasion. These might be exploited due to quantitative upregulation in tumors or the pathways being relatively specific for induced cell motility. These findings may increase our opportunities to limit tumor spread by targeting novel intracellular enzymes.